The invention relates to electrical circuits on automobile vehicles. It concerns in particular lighting circuits, the good operation inspection of which is a circulation safety factor. The short circuit risks of these circuits are important due to the geographical dispersion of controlled instruments on the vehicle.
The system that is offered provides safety at the circulation level because the driver is immediately warned of any lighting defect and at the level of the vehicle circuits which are not subject to destruction by fire in case of a short circuit. In addition, the method that is used, that is, inspection by a calculator, allows the realization of a sequential control, the principal advantage of which is to reduce the number of controls on the dashboard and to simplify the contruction, the repair, and the use of the vehicle.
The uses of the safety switch of the present invention are not limited to the lighting system; on the contrary, all the auxiliary electrical motors of the vehicle can be controlled through this method which, by its detection of short circuits and its maximum current limitation, avoids the overheating of motors that are fed when their shaft is mechanically locked. This allows suppression of the usual electrical safety devices, that is, limit switches or mechanical switches, and torque limiting devices.
The present invention is directed to solving several problems. The object of the present invention is to permit controlling the application of voltage or the isolation of a circuit regardless of its condition without modification of the components of the installation.
Another object of the present invention is to detect the condition of the controlled circuit, which may be either normal, open or short-circuited.
Still another object of the present invention is to report the condition of the circuit by a simple means allowing observation of whether the circuit is operating normally, whether it is open, or whether it is short-circuited. This may be obtained by providing a constantly lit warning light or flasher according to different sequences.
Yet another object of the present invention is to perform a safety function. The safety function includes limiting the current and periodically isolating and testing the short-circuited circuit. This safety function prevents the deterioration of the circuit and of its components. Thus, a circuit bearing hazardous short circuit is not rendered useless. As soon as the short circuit disappears, normal current supply is restored. Similarly, limiting the maximum current with the stated safety features presents certain advantages for incandescent lamp filaments, such as the reduction of thermal shocks and for electrical motors which are automatically provided with maximum torque limitation, maximum acceleration and locked induced heating.
On the other hand, the permanent inspection of circuits through a microprocessor which is contemplated by this system will facilitate all the applications of sequential control that can be considered.
The devices known to this day generally have only the following limited features. Control is obtained through a switch handled by the user. This control is either direct or indirect, which is to say that it acts through an electromagnetic relay on the power circuit. Safety is obtained through fuses in series or through a thermal circuit breaker. In some instances, no safety feature is planned. Defect reporting is obtained through a repeating warning light in some cases, such as for turn signal indicators. The checking of open circuits can also be accomplished during the rest period of these circuits by having a very weak current circulate there. This problem has so far received only elementary and partial solutions.
These known devices have several disadvantages relating to both control and safety.
For example, the ignition of an incandescent lamp, the filament of which is cold, provokes a current flash which is 50 to 100 times higher than the nominal current. This causes extensive wear of the switches that are used. Many switches and associated circuits are incapable of withstanding the elevated short-circuited current. To make the devices usable by the driver, it is necessary to regroup all these switches on an instrument cluster. These electromechanical systems are expensive, fragile and cumbersome. There remains, however, in addition to the instrument cluster, a large number of other switches on the dashboard, the proportions of which do not allow a worthy ergonomic location, that is, a good position in relation to the body of the user. Furthermore, the complex connecting wiring of these switches results in an expensive product, as well as in difficulties for service repairs and a lack of reliability.
However, these control components had the advantage of being, until now, the most simple and the most economical solution to the problem. The known devices also had significant safety disadvantages. The fuses, even when they are lagged and sized to withstand the initial elevated ignition of current incandescent lamps, are inefficient organs for the safety of the circuits in the event of a short circuit. Furthermore, experience shows that a user who suddenly has a short circuit on the road solves the failure by replacing the fuse without trying to find the cause of the short circuit. Often, the user rapidly exhausts his fuse supply and resorts to such means as an aluminum foil paper rolled around the melted fuse or just simply a suitably dimensioned metallic part such as a nail, a screw, or a paperclip. Fortunately, most of the short circuits on a vehicle disappear with road shocks and vehicle fires are not as numerous as they could be.
Thermal circuit breakers could be a good solution if their sizing was adapted to the short-circuited current which provides a short-circuit power which is 50 to 100 times higher than the controlled normal power.
This solution is declining for economic reasons. With respect to a driver's diagnosis or information, with the exception of turn signal indicators, generalized systems which inform the driver during operation of a defect in the device are nonexistent.